Provisioning and managing replicated data instances

ABSTRACT

A replicated database can be provisioned that provides primary and secondary replicas that can be provisioned in different data zones or geographical locations. The database can be installed on the primary replica, and both the primary and secondary replica can have installed a block level replication mechanism that allows any I/O operation to be replicated by between the primary and secondary replicas. Any failure or outage of the primary replica can be addressed by performing a failover operation to the secondary replica. A DNS name or other such approach can be used such that the name can be aliased to the secondary replica during a failover, such that there is no action needed on the part of the customer to utilize the “new” primary replica. The creation of the database and provisioning of the replicated instance can be initiated using a Web service call to a control environment. A replicated database can also be scaled according to storage or computing capacity with no disruption of service using a Web service call to the control environment.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/621,044, filed Sep. 15, 2012, now U.S. Pat. No. 9,336,292, which is acontinuation of U.S. patent application Ser. No. 12/606,093, filed Oct.26, 2009, now U.S. Pat. No. 8,335,765, which are hereby incorporatedherein by reference in their entireties for all purposes.

BACKGROUND

As an increasing number of applications and services are being madeavailable over networks such as the Internet, an increasing number ofcontent, application, and/or service providers are turning totechnologies such as cloud computing. Cloud computing, in general, is anapproach to providing access to electronic resources through services,such as Web services, where the hardware and/or software used to supportthose services is dynamically scalable to meet the needs of the servicesat any given time. A user or customer typically will rent, lease, orotherwise pay for access to resources through the cloud, and thus doesnot have to purchase and maintain the hardware and/or software toprovide access to these resources.

While aspects of various applications and resources can be adjusted andmanaged in the cloud, the data repositories upon which theseapplications and resources rely are not similarly adjustable or easilymanaged by a customer or other such user. Typically, performing taskssuch as provisioning and scaling data storage are tedious manualprocedures, in which a customer has to provide a database administrator(DBA) or similar expert user with configuration information andrequirements, such that the DBA can determine whether the configurationis valid. Further, there is no easy way for a customer to dynamicallyand/or automatically adjust the parameters for a database instance ormanage other such aspects of a data repository. In many cases, a datainstance will have backup and recovery mechanisms in place, but thesemechanisms often are in a single location or area such that they aresusceptible to failure or outages in that area.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments in accordance with the present disclosure will bedescribed with reference to the drawings, in which:

FIG. 1 illustrates an environment in which various embodiments can beimplemented;

FIG. 2 illustrates an example separation of a control plane and a dataplane that can be used in accordance with various embodiments;

FIG. 3 illustrates an example implementation for running a replicateddata instance across multiple data zones that can be used in accordancewith one embodiment;

FIG. 4 illustrates an example process for creating a replicated datainstance that can be used in accordance with one embodiment;

FIG. 5 illustrates an example process for creating a primary replicathat can be used in accordance with one embodiment; and

FIG. 6 illustrates an example process for creating a secondary replicathat can be used in accordance with one embodiment.

DETAILED DESCRIPTION

Systems and methods in accordance with various embodiments of thepresent disclosure may overcome one or more of the aforementioned andother deficiencies experienced in conventional approaches to managingaspects of data storage in an electronic environment. In particular,various embodiments provide a separate control environment, or controlplane, that can be used to enable a user to manage and/or alter variousaspects of a data environment, or data plane. This “self-service”functionality can be provided via a set of Web services, enabling theuser and control plane to act together as a virtual databaseadministrator (DBA). A user or customer can submit a request to thecontrol plane through one of a plurality of externally-visibleapplication programming interfaces (APIs), for example. Various APIs canbe used to perform specific functions with respect to a data repository,such as a relational database, in the data environment. A requestreceived to one of the APIs can be analyzed to determine the desiredaction(s) to be performed in the data plane, such as actions that adjustoperational or configuration parameters of a data store or data storageinstance. A component such as a workflow component can determine theappropriate tasks for the action, and cause the tasks to be executed inan appropriate order. At least one of these tasks typically will beperformed in the data environment, such as to adjust an aspect of arelational database.

In accordance with certain embodiments, such a system can provide forthe provisioning of a replicated data instance in the data environment.The provisioning can utilize a primary-secondary replication approach,with each of the primary and secondary replicas being provisioned in oracross one or more separate data zones, separate geographic locations,etc. The database replicas can run on separate data instances, eachattached to dedicated block storage volumes that are not shared acrossthe replicas.

In various embodiments, replication can be performed using a block-levelreplication mechanism, such as a Distributed Replicated Block Device(DRBD®) from Linbit of Vienna, Austria, or an Elastic Block Store (EBS),as provided by Amazon.com, Inc., of Seattle, Wash., which can mirror thecontent of block devices between servers and synchronously replicatedata across redundant systems. Each instance can run a kernel that has ablock-level replication mechanism kernel module installed for managingall input and output (I/O) operations for the data instance. All readsand writes can be executed at a primary replica, with the block-levelreplication mechanism replicating the information synchronously with thesecondary replica.

Both the primary and secondary replicas can have an external facing DNSname. Customers can reach the current primary replica using a DNS namesuch as DNS_primary. The DNS_primary name can alias or “cname” to theexternal DNS name of the (current) primary replica. When a primaryreplica fails or is otherwise unavailable, the secondary replica can bepromoted or failed over to become the new primary replica, whereby thecname for DNS_primary can update to the DNS name of the new primaryinstance. All writes are sent to the database on the current primaryreplica. When the primary instance receives a write, the information issynchronously written to the secondary replica. Upon successful write atboth places, the write can be deemed successful. All reads also areexecuted only at the primary replica in various embodiments.

FIG. 1 illustrates an example of an environment 100 for implementingaspects in accordance with various embodiments. As will be appreciated,although a Web-based environment is used for purposes of explanation,different environments may be used, as appropriate, to implement variousembodiments. The environment 100 shown includes both a testing ordevelopment portion (or side) and a production portion. The productionportion includes an electronic client device 102, which can include anyappropriate device operable to send and receive requests, messages, orinformation over an appropriate network 104 and convey information backto a user of the device. Examples of such client devices includepersonal computers, cell phones, handheld messaging devices, laptopcomputers, set-top boxes, personal data assistants, electronic bookreaders, and the like. The network can include any appropriate network,including an intranet, the Internet, a cellular network, a local areanetwork, or any other such network or combination thereof. Componentsused for such a system can depend at least in part upon the type ofnetwork and/or environment selected. Protocols and components forcommunicating via such a network are well known and will not bediscussed herein in detail. Communication over the network can beenabled by wired or wireless connections, and combinations thereof. Inthis example, the network includes the Internet, as the environmentincludes a Web server 106 for receiving requests and serving content inresponse thereto, although for other networks an alternative deviceserving a similar purpose could be used as would be apparent to one ofordinary skill in the art.

The illustrative environment includes at least one application server108 and a data store 110. It should be understood that there can beseveral application servers, layers, or other elements, processes, orcomponents, which may be chained or otherwise configured, which caninteract to perform tasks such as obtaining data from an appropriatedata store. As used herein the term “data store” refers to any device orcombination of devices capable of storing, accessing, and retrievingdata, which may include any combination and number of data servers,databases, data storage devices, and data storage media, in anystandard, distributed, or clustered environment. The application servercan include any appropriate hardware and software for integrating withthe data store as needed to execute aspects of one or more applicationsfor the client device, handling a majority of the data access andbusiness logic for an application. The application server providesaccess control services in cooperation with the data store, and is ableto generate content such as text, graphics, audio, and/or video to betransferred to the user, which may be served to the user by the Webserver in the form of HTML, XML, or another appropriate structuredlanguage in this example. The handling of all requests and responses, aswell as the delivery of content between the client device 102 and theapplication server 108, can be handled by the Web server. It should beunderstood that the Web and application servers are not required and aremerely example components, as structured code discussed herein can beexecuted on any appropriate device or host machine as discussedelsewhere herein. Further, the environment can be architected in such away that a test automation framework can be provided as a service towhich a user or application can subscribe. A test automation frameworkcan be provided as an implementation of any of the various testingpatterns discussed herein, although various other implementations can beused as well, as discussed or suggested herein.

The environment also includes a development and/or testing side, whichincludes a user device 118 allowing a user such as a developer, dataadministrator, or tester to access the system. The user device 118 canbe any appropriate device or machine, such as is described above withrespect to the client device 102. The environment also includes adevelopment server 120, which functions similar to the applicationserver 108 but typically runs code during development and testing beforethe code is deployed and executed on the production side and isaccessible to outside users, for example. In some embodiments, anapplication server can function as a development server, and separateproduction and testing storage may not be used.

The data store 110 can include several separate data tables, databases,or other data storage mechanisms and media for storing data relating toa particular aspect. For example, the data store illustrated includesmechanisms for storing production data 112 and user information 116,which can be used to serve content for the production side. The datastore also is shown to include a mechanism for storing testing data 114,which can be used with the user information for the testing side. Itshould be understood that there can be many other aspects that may needto be stored in the data store, such as for page image information andaccess right information, which can be stored in any of the above listedmechanisms as appropriate or in additional mechanisms in the data store110. The data store 110 is operable, through logic associated therewith,to receive instructions from the application server 108 or developmentserver 120, and obtain, update, or otherwise process data in responsethereto. In one example, a user might submit a search request for acertain type of item. In this case, the data store might access the userinformation to verify the identity of the user, and can access thecatalog detail information to obtain information about items of thattype. The information then can be returned to the user, such as in aresults listing on a Web page that the user is able to view via abrowser on the user device 102. Information for a particular item ofinterest can be viewed in a dedicated page or window of the browser.

Each server typically will include an operating system that providesexecutable program instructions for the general administration andoperation of that server, and typically will include a computer-readablemedium storing instructions that, when executed by a processor of theserver, allow the server to perform its intended functions. Suitableimplementations for the operating system and general functionality ofthe servers are known or commercially available, and are readilyimplemented by persons having ordinary skill in the art, particularly inlight of the disclosure herein.

The environment in one embodiment is a distributed computing environmentutilizing several computer systems and components that areinterconnected via communication links, using one or more computernetworks or direct connections. However, it will be appreciated by thoseof ordinary skill in the art that such a system could operate equallywell in a system having fewer or a greater number of components than areillustrated in FIG. 1. Thus, the depiction of the system 100 in FIG. 1should be taken as being illustrative in nature, and not limiting to thescope of the disclosure.

An environment such as that illustrated in FIG. 1 can be useful for aprovider such as an electronic marketplace, wherein multiple hosts mightbe used to perform tasks such as serving content, authenticating users,performing payment transactions, or performing any of a number of othersuch tasks. Some of these hosts may be configured to offer the samefunctionality, while other servers might be configured to perform atleast some different functions. The electronic environment in such casesmight include additional components and/or other arrangements, such asthose illustrated in the configuration 200 of FIG. 2, discussed indetail below.

Systems and methods in accordance with one embodiment provide arelational database service (“RDS”) that enables developers, customers,or other authorized users to easily and cost-effectively obtain andconfigure relational databases and other such data sources so that userscan perform tasks such as storing, processing, and querying relationaldata sets in a cloud. While this example is discussed with respect tothe Internet, Web services, and Internet-based technology, it should beunderstood that aspects of the various embodiments can be used with anyappropriate services available or offered over a network in anelectronic environment. Further, while the service is referred to hereinas a “relational database service,” it should be understood that such aservice can be used with any appropriate type of data repository or datastorage in an electronic environment. An RDS in this example includes atleast one Web service that enables users or customers to easily managerelational data sets without worrying about the administrativecomplexities of deployment, upgrades, patch management, backups,replication, failover, capacity management, scaling, and other suchaspects of data management. Developers are thus freed to developsophisticated cloud applications without worrying about the complexitiesof managing the database infrastructure.

An RDS in one embodiment provides a separate “control plane” thatincludes components (e.g., hardware and software) useful for managingaspects of the data storage. In one embodiment, a set of data managementapplication programming interfaces (APIs) or other such interfaces areprovided that allow a user or customer to make calls into the RDS toperform certain tasks relating to the data storage. The user still canuse the direct interfaces or APIs to communicate with the datarepositories, however, and can use the RDS-specific APIs of the controlplane only when necessary to manage the data storage or perform asimilar task.

FIG. 2 illustrates an example of an RDS implementation 200 that can beused in accordance with one embodiment. In this example, a computingdevice 202 for an end user is shown to be able to make calls through anetwork 206 into a control plane 208 to perform a task such as toprovision a data repository of the data plane 210. The user or anapplication 204 can access the provisioned repository directly throughan interface of a data plane 210. While an end user computing device andapplication are used for purposes of explanation, it should beunderstood that any appropriate user, application, service, device,component, or resource can access the interface(s) of the control planeand/or data plane as appropriate in the various embodiments. Further,while the components are separated into control and data “planes,” itshould be understood that this can refer to an actual or virtualseparation of at least some resources (e.g., hardware and/or software)used to provide the respective functionality.

The control plane 208 in this example is essentially a virtual layer ofhardware and software components that handles control and managementactions, such as provisioning, scaling, replication, etc. The controlplane in this embodiment includes a Web services layer 212, or tier,which can include at least one Web server, for example, along withcomputer-executable software, application servers, or other suchcomponents. The Web services layer also can include a set of APIs 232(or other such interfaces) for receiving Web services calls or requestsfrom across the network 206. Each API can be provided to receiverequests for at least one specific action to be performed with respectto the data environment, such as to provision, scale, clone, orhibernate an instance of a relational database. Upon receiving a requestto one of the APIs, the Web services layer can parse or otherwiseanalyze the request to determine the steps or actions needed to act onor process the call. For example, a Web service call might be receivedthat includes a request to create a data repository. In this example,the Web services layer can parse the request to determine the type ofdata repository to be created, the storage volume requested, the type ofhardware requested (if any), or other such aspects. Information for therequest can be written to an administration (“Admin”) data store 222, orother appropriate storage location or job queue, for subsequentprocessing.

A Web service layer in one embodiment includes a scalable set ofcustomer-facing servers that can provide the various control plane APIsand return the appropriate responses based on the API specifications.The Web service layer also can include at least one API service layerthat in one embodiment consists of stateless, replicated servers whichprocess the externally-facing customer APIs. The Web service layer canbe responsible for Web service front end features such as authenticatingcustomers based on credentials, authorizing the customer, throttlingcustomer requests to the API servers, validating user input, andmarshalling or unmarshalling requests and responses. The API layer alsocan be responsible for reading and writing database configuration datato/from the administration data store, in response to the API calls. Inmany embodiments, the Web services layer and/or API service layer willbe the only externally visible component, or the only component that isvisible to, and accessible by, customers of the control service. Theservers of the Web services layer can be stateless and scaledhorizontally as known in the art. API servers, as well as the persistentdata store, can be spread across multiple data centers in a geographicalregion, or near a geographical location, for example, such that theservers are resilient to single data center failures.

The control plane in this embodiment includes what is referred to hereinas a “sweeper” component 214. A sweeper component can be any appropriatecomponent operable to poll various components of the control plane orotherwise determine any tasks to be executed in response to anoutstanding request. In this example, the Web services layer might placeinstructions or information for the “create database” request in theadmin data store 222, or a similar job queue, and the sweeper canperiodically check the admin data store for outstanding jobs. Variousother approaches can be used as would be apparent to one of ordinaryskill in the art, such as the Web services layer sending a notificationto a sweeper that a job exists. The sweeper component can pick up the“create database” request, and using information for the request cansend a request, call, or other such command to a workflow component 216operable to instantiate at least one workflow for the request. Theworkflow in one embodiment is generated and maintained using a workflowservice as is discussed elsewhere herein. A workflow in general is asequence of tasks that should be executed to perform a specific job. Theworkflow is not the actual work, but an abstraction of the work thatcontrols the flow of information and execution of the work. A workflowalso can be thought of as a state machine, which can manage and returnthe state of a process at any time during execution. A workflowcomponent (or system of components) in one embodiment is operable tomanage and/or perform the hosting and executing of workflows for taskssuch as: repository creation, modification, and deletion; recovery andbackup; security group creation, deletion, and modification; usercredentials management; and key rotation and credential management. Suchworkflows can be implemented on top of a workflow service, as discussedelsewhere herein. The workflow component also can manage differencesbetween workflow steps used for different database engines, such asMySQL, as the underlying workflow service does not necessarily change.

In this example, a workflow can be instantiated using a workflowtemplate for creating a database and applying information extracted fromthe original request. For example, if the request is for a MySQL®Relational Database Management System (RDBMS) instance, as opposed to anOracle® RDBMS or other such instance, then a specific task will be addedto the workflow that is directed toward MySQL instances. The workflowcomponent also can select specific tasks related to the amount ofstorage requested, any specific hardware requirements, or other suchtasks. These tasks can be added to the workflow in an order of executionuseful for the overall job. While some tasks can be performed inparallel, other tasks rely on previous tasks to be completed first. Theworkflow component or service can include this information in theworkflow, and the tasks can be executed and information passed asneeded.

An example “create database” workflow for a customer might includestasks such as provisioning a data store instance, allocating a volume ofoff-instance persistent storage, attaching the persistent storage volumeto the data store instance, then allocating and attaching a DNS addressor other address, port, interface, or identifier which the customer canuse to access or otherwise connect to the data instance. In thisexample, a user is provided with the DNS address and a port address tobe used to access the instance. The workflow also can include tasks todownload and install any binaries or other information used for thespecific data storage technology (e.g., MySQL). The workflow componentcan manage the execution of these and any related tasks, or any otherappropriate combination of such tasks, and can generate a response tothe request indicating the creation of a “database” in response to the“create database” request, which actually corresponds to a data storeinstance in the data plane 210, and provide the DNS address to be usedto access the instance. A user then can access the data store instancedirectly using the DNS address and port, without having to access or gothrough the control plane 208. Various other workflow templates can beused to perform similar jobs, such as deleting, creating, or modifyingone of more data store instances, such as to increase storage. In someembodiments, the workflow information is written to storage, and atleast one separate execution component (not shown) pulls or otherwiseaccesses or receives tasks to be executed based upon the workflowinformation. For example, there might be a dedicated provisioningcomponent that executes provisioning tasks, and this component might notbe called by the workflow component, but can monitor a task queue or canreceive information for a provisioning task in any of a number ofrelated ways as should be apparent.

As mentioned, various embodiments can take advantage of a workflowservice that can receive requests or calls for a current state of aprocess or task, such as the provisioning of a repository, and canreturn the current state of the process. The workflow component and/orworkflow service do not make the actual calls or requests to performeach task, but instead manage the state and configuration informationfor the workflow that enables the components of the control plane todetermine the next task to be performed, and any information needed forthat task, then generate the appropriate call(s) into the data planeincluding that state information, whereby a component of the data planecan make the call to perform the task. Workflows and tasks can bescheduled in parallel in order to increase throughput and maximizeprocessing resources. As discussed, the actual performing of the taskswill occur in the data plane, but the tasks will originate from thecontrol plane. For example, the workflow component can communicate witha host manager, which can make calls into the data store. Thus, for agiven task a call could be made to the workflow service passing certainparameters, whereby the workflow service generates the sequence of tasksfor the workflow and provides the current state, such that a task forthe present state can be performed. After the task is performed (orotherwise resolved or concluded), a component such as the host managercan reply to the service, which can then provide information about thenext state in the workflow, such that the next task can be performed.Each time one of the tasks for the workflow is performed, the servicecan provide a new task to be performed until the workflow is completed.Further, multiple threads can be running in parallel for differentworkflows to accelerate the processing of the workflow.

The control plane 208 in this embodiment also includes at least onemonitoring component 218. When a data instance is created in the dataplane, information for the instance can be written to a data store inthe control plane, such as a monitoring data store 220. It should beunderstood that the monitoring data store can be a separate data store,or can be a portion of another data store such as a distinct set oftables in an Admin data store 222, or other appropriate repository. Amonitoring component can access the information in the monitoring datastore to determine active instances 234 in the data plane 210. Amonitoring component also can perform other tasks, such as collectinglog and/or event information from multiple components of the controlplane and/or data plane, such as the Web service layer, workflowcomponent, sweeper component, and various host managers. Using suchevent information, the monitoring component can expose customer-visibleevents, for purposes such as implementing customer-facing APIs. Amonitoring component can constantly monitor the health of all therunning repositories and/or instances for the control plane, detect thefailure of any of these instances, and initiate the appropriate recoveryprocess(es).

Each instance 234 in the data plane can include at least one data store226 and a host manager component 228 for the machine providing access tothe data store. A host manager in one embodiment is an application orsoftware agent executing on an instance and/or application server, suchas a Tomcat or Java application server, programmed to manage tasks suchas software deployment and data store operations, as well as monitoringa state of the data store and/or the respective instance. A host managerin one embodiment listens on a port that can only be reached from theinternal system components, and is not available to customers or otheroutside entities. In some embodiments, the host manager cannot initiateany calls into the control plane layer. A host manager can beresponsible for managing and/or performing tasks such as setting up theinstances for a new repository, including setting up logical volumes andfile systems, installing database binaries and seeds, and starting orstopping the repository. A host manager can monitor the health of thedata store, as well as monitoring the data store for error conditionssuch as I/O errors or data storage errors, and can restart the datastore if necessary. A host manager also perform and/or mange theinstallation of software patches and upgrades for the data store and/oroperating system. A host manger also can collect relevant metrics, suchas may relate to CPU, memory, and I/O usage.

The monitoring component can communicate periodically with each hostmanager 228 for monitored instances 234, such as by sending a specificrequest or by monitoring heartbeats from the host managers, to determinea status of each host. In one embodiment, the monitoring componentincludes a set of event processors (or monitoring servers) configured toissue commands to each host manager, such as to get the status of aparticular host and/or instance. If a response is not received after aspecified number of retries, then the monitoring component can determinethat there is a problem and can store information in the Admin datastore 222 or another such job queue to perform an action for theinstance, such as to verify the problem and re-provision the instance ifnecessary. The sweeper can access this information and kick off arecovery workflow for the instance to attempt to automatically recoverfrom the failure. The host manager 228 can act as a proxy for themonitoring and other components of the control plane, performing tasksfor the instances on behalf of the control plane components.Occasionally, a problem will occur with one of the instances, such asthe corresponding host, instance, or volume crashing, rebooting,restarting, etc., which cannot be solved automatically. In oneembodiment, there is a logging component (not shown) that can log theseand other customer visibility events. The logging component can includean API or other such interface such that if an instance is unavailablefor a period of time, a customer can call an appropriate “events” orsimilar API to get the information regarding the event. In some cases, arequest may be left pending when an instance fails. Since the controlplane in this embodiment is separate from the data plane, the controlplane never receives the data request and thus cannot queue the requestfor subsequent submission (although in some embodiments this informationcould be forwarded to the control plane). Thus, the control plane inthis embodiment provides information to the user regarding the failureso the user can handle the request as necessary.

As discussed, once an instance is provisioned and a user is providedwith a DNS address or other address or location, the user can sendrequests “directly” to the data plane 210 through the network using aJava Database Connectivity (JDBC) or other such client to directlyinteract with that instance 234. In one embodiment, the data plane takesthe form of (or at least includes or is part of) a computing cloudenvironment, or a set of Web services and resources that provides datastorage and access across a “cloud” or dynamic network of hardwareand/or software components. A DNS address is beneficial in such adynamic cloud environment, as instance or availability failures, forexample, can be masked by programmatically remapping a DNS address toany appropriate replacement instance for a use. A request received froma user 202 or application 204, for example, can be directed to a networkaddress translation (NAT) router 224, or other appropriate component,which can direct the request to the actual instance 234 or hostcorresponding to the DNS of the request. As discussed, such an approachallows for instances to be dynamically moved, updated, replicated, etc.,without requiring the user or application to change the DNS or otheraddress used to access the instance. As discussed, each instance 234 caninclude a host manager 228 and a data store 226, and can have at leastone backup instance or copy in persistent storage 230. Using such anapproach, once the instance has been configured through the controlplane, a user, application, service, or component can interact with theinstance directly through requests to the data plane, without having toaccess the control plane 232. For example, the user can directly issuestructured query language (SQL) or other such commands relating to thedata in the instance through the DNS address. The user would only haveto access the control plane if the user wants to perform a task such asexpanding the storage capacity of an instance. In at least oneembodiment, the functionality of the control plane 208 can be offered asat least one service by a provider that may or may not be related to aprovider of the data plane 210, but may simply be a third-party servicethat can be used to provision and manage data instances in the dataplane, and can also monitor and ensure availability of those instancesin a separate data plane 210.

As discussed, one advantage to providing the functionality of a controlplane as a Web service or other such service is that the control planefunctions as a virtual database administrator (DBA) and avoids the needfor a human DBA to perform tasks such as provisioning data. Provisioningdata is presently a tedious manual procedure, requiring a DBA to receivethe necessary configuration information, determine whether theconfiguration is valid, optimize and tune the instance, and performother such tasks, which take a significant amount of time and effort.Further, such an approach provides many opportunities for error, whichmight not be discovered until after data is lost. Using a control planeor service as described herein, a user or customer can instead submit acall including information such as a type of hardware and a version of adatabase product. The control plane or service can then perform thenecessary tasks to create, delete, modify, expand, or otherwise modify adata store or data storage instance. The control plane also can supportseveral different database engines in a consistent fashion, withoutrequiring a DBA to be an expert in each of the engines. Onceprovisioned, the user has native access to the data instance(s), and cansimply point existing applications (such as MySQL applications) to theDNS address or other location information for the particular instance.There is no restriction or modification of query models or other suchfunctionality, as a user can continue to use applications built onMySQL, Oracle, or other database technology.

Systems and methods in accordance with various embodiments enablecustomers to utilize Web services, or a similar such approach, to createone or more replicated database instances in a cloud computing orsimilar environment, providing a highly durable and highly availabledata solution. When a customer creates a replicated database instance invarious embodiments, the customer data is synchronously replicated usinga primary-secondary replication model. In some embodiments, the replicascan be located in different physical locations, such as in differentdata zones. Each data “zone” can refer to one or more data centers, orgroups of data servers, for example, located within a specificgeographical area, with different zones being located at or arounddifferent geographic locations. An RDS instance then can tolerate thefailure of one of the data zones, as another data zone at a differentgeographic location can likely avoid the failure, except in the case ofa large catastrophic event. In some cases a data center can spanmultiple data zones, but data replicas within a given data center can beinstantiated in different zones. Many other variations are possible,such as overlapping zones, zones at multiple geographic locations, etc.If a primary replica fails or otherwise becomes unavailable, the RDSsystem can quickly and automatically failover to the secondary replica,resulting in very little downtime or data unavailability.

In one embodiment, a customer is able to create a replicated databaseinstance by calling a specified interface of the Web services layer ofthe control plane, such as is discussed with respect to FIG. 2. Forexample, a customer can call a “CreateDBInstance” API specifying aspectssuch as the instance class, allocated storage, database engine, etc., asthe customer would to create a non-replicated data instance. Whencreating a replicated instance, the customer can include at least oneadditional parameter, such as a “Replicated” or similar parameter, witha value set to “true” or any other appropriate value indicating that thecreated instance should be replicated. In some embodiments, the value isset to “false” by default such that non-replicated instances are createdunless otherwise specified by the customer. In some embodiments, onlycertain customers have the ability to create replicated instances, suchas a customer who pays for a certain level of service, etc.

In some embodiments, a customer also can select whether the secondaryreplica is created in a different data zone than the primary replica.The customer in some embodiments also can be allowed to select one ormore specific data zones for the instances, or an ordered list, forexample, while in other embodiments customers are not able to select thedata zone for at least the primary replica. If a customer specifies twodata zones and one of the data zones becomes unavailable for an extendedperiod of time, for example, the durability requirements in someembodiments would cause another replica to be generated in a third datazone, and so on. This could require management and updating of ordersdata zone lists for multiple customers, which can complicate the userexperience without providing any significant benefit. Further, it can beeasier for applications to spread the associated application fleetacross data zones, such that there can be some application fleetslocated in the same data zone as the secondary replica.

In some embodiments, a customer can call a “DescribeDBInstance” orsimilar API for the replicated data instance, whereby RDS can listinformation such as the endpoint DNS name of the primary replica and thedata zone in which the primary replica is currently located. Customerscan still communicate with the RDS instance using conventionalapproaches that would be used for a single data zone, as customers canreceive the endpoint DNS name of a data store as soon as the status ofthe RDS instance is “Available,” for example, and connect to theinstance using the endpoint DNS name. In the event of a replica failure,RDS can failover the database to the corresponding secondary replica,and the endpoint DNS name can will be aliased to the new primaryreplica. The database endpoint DNS name remains a constant in manyembodiments, not changing during the lifetime of the replicatedinstance.

In some embodiments customers can be provided with the ability toconvert a non-replicated instance to a replicated instance, such as bycalling a “ModifyDBInstance” or similar API with the Replicatedparameter set to “true.” This can cause the database to be converted toa replicated instance at an appropriate time, such as during the nextmaintenance window or immediately after the request, as may depend onthe API call parameters, etc.

Various embodiments take advantage of a block-level replicationmechanism, such as a kernel module that implements a share-nothing,replicated storage solution mirroring the content of block devicesbetween servers. A block-level replication mechanism (“BLRM”) can workon top of block devices (i.e., hard disks or logical volumes). It uses aprimary-slave replication architecture wherein the primary replicadirects all the updates to the underlying block device. All input andoutput (I/O) requests to the block device are intercepted by the BLRMkernel module, with all write operations being automatically andsynchronously replicated. BLRM provides inherent failure detection ofpeer devices, and invokes appropriate recovery handlers when a peer nodeis unreachable. BLRM also can automatically resynchronize a temporarilyunavailable node to the latest version of the data, in the background,without interfering with data access at the primary replica. BLRM usesgeneration identifiers (“GIs”) to identify generations of replicateddata, whereby BLRM can determine aspects such as whether the two nodesare members of the same replica pair, the direction of backgroundre-synchronization (if necessary), and whether partial or fullre-synchronization is needed. A BLRM driver can start a new generationat any appropriate time, such as during the initialization of a replicapair, when a disconnected standby replica is switching to the primaryreplica, or when a resource in the primary role is disconnecting fromthe secondary replica. While a block-level replication mechanism is usedherein as an example for purposes of explanation, it should beunderstood that any other appropriate block-level technology ormechanism can be used within the scope of various embodiments.

As discussed, RDS data instances in various embodiments can be builtupon one or more systems or platforms. For example, the instances can bebuilt upon a virtual computing environment that enables a customer toutilize Web services or another appropriate approach to launch instanceswith a variety of operating systems and manager those instances. Anexample of a Web service providing such a virtual computing environmentis the Elastic Compute Cloud (EC2) service offered by Amazon.com, Inc.The data instances also can be built upon a block-level storagemechanism that can provide off-instance storage that persistsindependently of the life of an instance. A block store mechanism canprovide storage volumes that can be attached to an instance and exposedas a device within the instance. An example of a block store platform isprovided in co-pending U.S. patent application Ser. No. 12/188,949,filed Aug. 8, 2008, entitled Managing Access of Multiple ExecutingPrograms to a Non-Local Block Data Storage,” which is herebyincorporated herein by reference. A logical volume (e.g., LVM layer) canbe built on top of the block storage volumes and an appropriate filesystem, such that the customer database can run on top of the LVM/filesystem layer. For a replicated database in one embodiment, BLRM can runon top of the LVM layer. BLRM in such an embodiment will intercept allI/O requests and send those requests to the logical volume, which inturn can split the requests across multiple block storage volumes. Theuse of a logical volume can provide the ability to handle multiple blockstorage E volumes, as well as the ability to easily expand storage, etc.Layering BLRM on top of LVM also can allow write operations to bereplicated across the replicas.

FIG. 3 illustrates an example of a mechanism 300 for implementing aprimary-secondary replication model to provide a replicated RDSinstance. In this example, the primary replica 310 and the secondaryreplica 312 are located in different data zones (1 and 2) of the dataplane 308, or database environment. Each replica is built on top of theblock storage mechanism, here illustrated as a BLRM layer 318, 322 formanaging I/O to a block store 320, 322 for each replica. The componentsof the control plane 306, such as may be similar to those discussed withrespect to FIG. 2, are able to create the replicated RDS instance byissuing configuration commands to the local host manager 314, 316, forexample, which can perform the necessary setup operations. As seen inthe figure, a block-level mechanism such as BLRM 318, 322 is positionedto intercept all I/O requests at the block device level, and writeinformation for the requests to the local disks and the remote disks320, 324. In this example, the database 318 (e.g., SQL) is run only inthe primary replica 310, and all clients 302 run their databasetransactions on the primary replica 310 (via an appropriate network304). The database 318 is not run on the secondary replica 312, and afile system also might not be mounted on the secondary replica, as thedatabase will generally not be aware of the updates in the underlyingdevice.

Each database client 302 can automatically discover the current primaryreplica using an RDS database DNS endpoint name, which can alias to thehost name of the primary replica 310. By using DNS to discover thecurrent primary replica, compatibility can be maintained with existingdatabase clients, such as native MySQL clients, JDBC, PHP, C#, andHaskell, for example. While DNS caching can potentially cause clients toattempt to connect to an old primary replica, a client will not be ableto talk to the database by connecting to a secondary replica, as nodatabase is run in the secondary replica. The customer can then know toobtain the proper DNS information.

An example of a process 400 for creating a replicated RDS instance for acustomer in accordance with one embodiment is illustrated in FIG. 4.While the term “customer” is used herein to refer to the “owner” ofdata, or a data store or instance hosted by the RDS system, it should beunderstood that the term customer is merely an example, and that anyappropriate user or developer can be allowed to access the control planeand data plane in the various embodiments. Further, while an embodimentrelating to the control of a data environment is described, it should beunderstood that similar approaches can be used to control and/or managevarious other components, devices, applications, services, or other suchresources in an environment separate from the control environment. Thesteps of this process are presented as examples for a particularembodiment, but it should be understood that additional, fewer, and/oralternative steps can be performed in different orders, and/or inparallel or concurrently, within the scope of the various embodiments.

In this example, a customer calls a CreateDBInstance or similar API 402,wherein the components of the Web service tier can analyze the call andcause the database creation parameters supplied by the customer to bestored to the Admin data store 404. The lifecycle of the database can bemarked with a value such as “CREATING,” upon successfully committing therecords to the Admin data store, with a change state of “PENDING” suchthat the task or job of creating the database will be picked up by asweeper component. The Web service tier does not directly call theworkflow system to kickoff the activity in this embodiment to avoid thetwo-phase task of launching the activity then verifying that workflowstarted the task. By simply saving the request for retrieval by asweeper, no workflow activities will be lost.

As discussed previously, the sweeper periodically polls the Admin datastore for new jobs. A database record with a lifecycle and change stateof CREATING and PENDING, for example, can cause the sweeper to launch a“CreateDatabase” or similar workflow 406. As an initial task of theworkflow, the change state of the database can be updated to a valuesuch as “APPLYING,” whereby other sweepers are aware the change is inprogress. Other primary tasks of the workflow include creating aninstance that will act as the primary replica 408, creating thesecondary replica from the primary replica 410, and connecting thesecondary replica with the primary replica 412. Once the replicas areconnected and available, the RDS instance can be exposed to the customerand accessible using the DNS name 414. In various embodiments, a scalecompute for the secondary replica is performed “behind the scenes,”whereby the secondary replica can be scaled before connecting thereplicas for replication and/or failover.

FIG. 5 illustrates an example of a portion 500 of such a process thatcan be used to create the primary replica in accordance with oneembodiment. As discussed, a workflow can take the initial steps toprovision all the resources that makeup an RDS instance. For example, adata instance is created for the primary host 502, such as by usingRDS-specific machine images. The block storage volume can be allocatedand attached for the primary host 504. Volumes can be requested based atleast in part upon configuration information specifying aspects such asthe maximum size of an individual volume and the desired minimum numberof volumes. A single volume can be used when reserved IOPS areguaranteed. Once each of the core resources becomes available, theworkflow attaches the block storage volumes to the data instanceallocated for the primary replica.

In some embodiments, a security group is created that performs functionssimilar to a firewall for a customer database. A security group canenable a customer to define a range of addresses such as Internetprotocol (IP) addresses, for example, that can communicate with thedatabase, or define which data instances can communicate with thedatabase.

The workflow can cause a host manager to be installed and started 506,such as by downloading the host manager, verifying the checksum orotherwise validating the download, and calling an appropriate installinterface, such as a Tomcat install application API. Once the hostmanager is successfully started after installation, the data instancecan have the functionality needed to install the database engine andsetup the customer database.

The workflow can request various actions to be performed by the hostmanger for the primary replica once the primary replica is running. Forexample, the host manager can request that the block storage volumes bemounted and the file system prepared 508. In certain embodiments, themounting of block storage volumes and building of the file system areperformed for each of two roles: a binary role and a data role. In oneembodiment, the control plane sends a storage configuration file (e.g.,an XML file), which provides the information to the host manager aboutthe mount points and volumes to be used for each role. Using thisinformation, the host manager can create the physical devices for allvolumes provisioned for a given role, and can create a logical volumethat stripes the data across these devices for each role. Once thelogical volumes are created 510, the host manager can create the BLRMconfiguration information by installing a BLRM configuration file, withitself as the only replica, and starting the BLRM kernel module. OnceBLRM is started using the configuration information 512, BLRM canautomatically handle all the I/O accesses to the data volume.

The workflow then can install a packet manager (e.g., RPM) publicsigning key, or other security mechanism, to the host manager for theprimary replica. The host manager for the primary replica then candownload and install the database engine 514, such as by the hostmanager on the data instance downloading and verifying the signedinformation, followed by an unpacking, installation, and launching ofthe package. Subsequently, the host manager for the primary replica caninstall a blank database to be used as the basis of the customerdatabase. By starting with an RDS-specific blank database, permissionsand tables used for management can be easily applied. The host managercan create the customer database, change the root password for thedatabase, and create a master database user as specified in the customerrequest 516. The workflow then can start the database 518 (e.g., MySQL).

With the database started, the BLRM resource can be disconnected and thebitmap cleared. The workflow can cause snapshots to be captured for theblock storage volumes of the primary host, and the host manager of theprimary instance can be instructed to create a new general interface.The host manger then can be instructed to install a new BLRMconfiguration file with the secondary hostname, and can reload theconfiguration information.

Once at least some of the above tasks of the example workflow arecomplete, the workflow can move on to tasks directed to building thesecondary replica. FIG. 6 illustrates steps of an example process 600for creating at least one secondary or standby replica that can be usedin accordance with various embodiments. As a first task, the blockstorage volumes can be created from the block storage snapshots of thedata volume for the primary replica 602, and a volume can be created forbinaries. The workflow then can cause the data instance to be launched,and the allocated volumes attached 604. As discussed, a scale computecan be performed for the secondary replica before connection with theprimary replica. The host manager then can be launched for the secondaryreplica 606. Once the host manager is running for the secondary replica,the workflow can call the host manager to setup the secondary instance.During the setup process, the host manager can setup the volumes 608,install the BLRM configuration file with the appropriate primary andsecondary replica configuration 610, determine whether BLRM is installedand start the kernel module, then startup the BLRM handler 612. At thispoint, the primary and secondary replicas should be connected andsynchronizing from the point that the clear-bitmap call was issued. Theworkflow then can mark the database as “Available” in the Admin datastore, and make the instance available to the customer 614.

Once the primary and secondary replicas for an instance are running andavailable to the customer, the customer can perform any of severalactions with respect to the instance. For example, a customer might senda request, to the API or command line tool of the Web services layer, todescribe one or more databases. The Web Service can immediately fulfillthe request by querying the Admin data store for the current state ofthe customer database(s) specified in the request. In the event ofpending modifications, the current and modified values can be displayedto the customer.

In some situations, a customer might call an API such as a“RebootDBInstance” API in order to reboot a customer database. In oneembodiment, this API only enables customers to reboot the databaseengine and not the RDS instance. The Web services layer can storeinformation to the Admin data store (or another such job queue) wherebythe sweeper can pick up information to start a workflow. The workflowcan call the host manager of the primary replica to restart thedatabase. The implementation of this API in various embodiments does notdiffer between a replicated and non-replicated instance.

A customer might send a request to delete a customer database using anAPI or command line tool, for example, whereby the components of thecontrol plane can be instructed to prepare the deletion. Afterverification of the credentials and the request parameters, for example,the components of the Web services tier can, for example, verify thatthe customer database can be deleted at the present time, such as therethe lifecycle is not in a CREATING or DELETING state. The componentsalso can update the appropriate record for the customer database in theAdmin data store to a lifecycle state of DELETING and change state ofPENDING. The workflow sweeper, which periodically polls for tasks to becompleted, can identify that the database should be deleted, due to thechange state of PENDING, and can launch a workflow instance to completethe deletion. A first action or task of the workflow can be to updatethe change state of the database to APPLYING, such that other Sweepersare aware the change is in progress.

The workflow instance can pull any remaining event logs and release theresources allocated for primary and secondary replicas. For example, theworkflow can direct the RDS event processor to pull events from the RDSinstance, then shut down the database and un-mount the file system inthe primary replica. The workflow can direct a snapshot to be taken ofthe database if a final snapshot was requested by the customer, or ifpolicy otherwise dictates. The instance can be de-registered by callingthe RDS event processor API to ensure that the event processor systemdoes not monitor the instance anymore. The DNS name can be deleted, andthe block storage volumes and data instances released. The workflow cancomplete deletion by updating the record for this customer database inthe Admin data store to a status of DELETED, whereby the record can bemoved into the records archive and the record deleted.

It also sometimes can be necessary or desirable for a customer to scalethe storage and/or computing capacity allocated for an instance. Whenscaling storage, for example, volumes can be added to both the primaryand secondary replicas, with the LVM being extended. On the primaryreplica, the BLRM handler can be called to extend the block device toinclude the new volumes under the control of the block device, and thefile system can be resized.

In particular, new block storage volume(s) can be provisioned accordingto current volume configuration parameters for both the primary replicaand the secondary replica. A “ScaleStorage” or similar API can beinvoked for the host manager on both instances, which can cause thephysical device to be created and the new volumes added to the existingvolume group. The host manager can rebalance the space in the volumegroup, such as by moving LVM physical extents from one physical volume(e.g., block storage volume) to another physical volume. The logicalvolume also can be extended to encompass the new space. Once theScaleStorage function completes, the workflow can call an interface suchas a “primaryScaleStorage” API for the host manager on the primaryinterface, which can cause the BLRM block device layer to be extended touse the new space. Once BLRM resizing is complete, the filesystem can beresized. If there are no remaining updates, the record for the customerdatabase in the Admin data store can be set to a lifecycle state of“AVAILABLE”, and the change state updated to “NONE”. The resizedinstance can then be utilized by the customer. If the primary orsecondary replica is unreachable during the scaling process, theworkflow can abort and leave the state in “MODIFYING,” for example, andretry at a later time.

When scaling the computing capacity, various embodiments enable acustomer to adjust a “compute class” for the instance, with each classhaving a specified compute capacity allocated. In certain embodiments,the secondary replica is scaled first, with the system then switchingover to the secondary replica, such as by using a failover process,whereby the secondary replica becomes the new primary replica. Thecompute node of the old primary replica then can be scaled as necessary,and the old primary replica can function as the new secondary replica.By scaling the secondary replica first and staging a failover, forexample, the replicated instance can experience less downtime that mightotherwise occur when scaling an instance class in a single data zone.

The following presents a specific example of a process for scaling adatabase instance in which the replicated instance has a primary replicaP and a secondary replica S. New instances (e.g., P_new and S_new) canbe provisioned for both the primary and the secondary replica, with thenew instance class, and with the same security group as the existinginstances. P_new and S_new can be created in the same data zones as Pand S, respectively. The status for the RDS instance in the Admin datastore can be updated to a value such as “IN_MODIFICATION”. The instanceidentifiers can be de-registered from the event processors such thatwhen the workflow takes the database down for scaling, recovery of theprimary and/or secondary replica is not triggered. The status for thesecondary instance can be updated to a value such as “IN_MODIFICATION.”On the secondary replica, the host manager can be requested to ceaseusing the existing block storage mechanism by, for example, stopping thedatabase, disconnecting from the primary instance (e.g., by issuing aBLRM disconnect command), unmounting all file systems, and deactivatingall volume groups. The block storage volumes can be detached from S andattached to S_new. The host manager then can be installed on S_new, andcan be requested to activate the volume groups. The primary replica thencan be terminated, such as by shutting down the database and unmountingthe volumes, and all the block storage volumes can be detached. Thefailover to S_new can be initiated by pointing the database endpoint toS_new, thus making S_new the new primary replica. The host manager onS_new can be requested to mount the file system, and credentials (e.g.,the RPM public key) can be sent to the host manager on the new instance.The host manager on S_new then can be requested to start the database,and the database can be marked as AVAILABLE. At this stage the databaseis ready to use, even though the secondary is still under creation. As anext step, the P_new instance can be started and the block storagevolumes that were previously attached to P can be attached to P_new. Thehost manager can be installed on P_new, and the BLRM configuration fileinstalled. In this embodiment, no file system is mounted on P_new atthis time. A command then can be issued to the host manager on S_new toconnect S_new with P_new, as well as to verify the connection status.The scaled replicas then can be provided for access by the customers.

Embodiments also can allow users to backup information in theirinstances, such as by creating snapshots or other point-in-time backups.For example, RDS can enable customers to create snapshots of theirinstances and create new instances from these snapshots. The snapshotsalso can be used to perform point-in-time recovery for a replicateddatabase. To create snapshots of a non-replicated instance, the workfloweffectively suspends I/O to the database volumes, takes blockstorage-level snapshots of the volumes attached to the instance, andun-suspends the volume. When creating snapshots for replicatedinstances, the snapshots can be taken at the secondary replica. Forthis, the secondary replica can be temporarily disconnected and asnapshot taken of all the block storage volumes. After taking thesnapshot, the secondary replica can be reconnected. By enabling backups,customers have the ability to restore an instance to a given point intime as long as the time is within the past X days, where X is theretention period for the customer.

When a customer enables backups in a non-replicated instance, snapshotscan be taken for the instance at regular intervals, such as every dayduring a backup window, and the logs can be backed up at otherintervals, such as every five minutes. When a customer wants to restorethe instance to a specific point in time, such as t₁, an instance can becreated from a snapshot with a time closest to, but before, the desiredpoint in time, and the logs can be used to roll the state forward tomirror that point in time. In a replicated instance, the snapshots canbe taken on the secondary replica while the logs are backed up from theprimary replica.

In one embodiment, all communication channels to the host managers aresecured using a hypertext transfer protocol over a secure socket layer(SSL). Each application server hosting a host manager application can bestarted using scripts at boot-up of an instance. Before starting theapplication server engine, a script can be executed that generates aself-signed certificate and installs the certificate to enable the SSLcommunication channel(s). SSL communication is used in one embodimentfor encrypting the communication channel and not for clientauthentication. Client authentication is instead achieved with apublic/private key signature embedded in each request, such that in oneembodiment all clients sign query string parameters using a private key.This signature can be validated by a custom interceptor, which can bedeployed with the application server for the host manager. Further, asecurity group (i.e., firewall rules) can be established for eachmonitored instance in the data plane such that only hosts sitting in agiven network or secure group can communicate using the host managerport. Secure information and credentials (such as private keys) can bestored in an appropriate keystore, which can provide for functionalitysuch as key management and rotation.

As discussed, the log files also can be backed up in a similar fashion.The logs can be used to perform tasks such as replaying varioustransactions in case the data files have to be restored. The engine logscan be copied to an appropriate storage location, such that previouslybacked-up log files can be obtained using a simple list command. A hostmanager will use this result to determine whether there are logs thatneed to be copied. For example, the host manager can request a bucketlist to obtain the list of log files written such that the last sequencecan be backed up. If new logs have been created, it can first bedetermined that the logs are not actively being written to by a databaseengine, and then the logs can be copied and the copying verified to havebeen performed successfully.

As discussed above, the various embodiments can be implemented in a widevariety of operating environments, which in some cases can include oneor more user computers, computing devices, or processing devices whichcan be used to operate any of a number of applications. User or clientdevices can include any of a number of general purpose personalcomputers, such as desktop or laptop computers running a standardoperating system, as well as cellular, wireless, and handheld devicesrunning mobile software and capable of supporting a number of networkingand messaging protocols. Such a system also can include a number ofworkstations running any of a variety of commercially-availableoperating systems and other known applications for purposes such asdevelopment and database management. These devices also can includeother electronic devices, such as dummy terminals, thin-clients, gamingsystems, and other devices capable of communicating via a network.

Various aspects also can be implemented as part of at least one serviceor Web service, such as may be part of a service-oriented architecture.Services such as Web services can communicate using any appropriate typeof messaging, such as by using messages in extensible markup language(XML) format and exchanged using an appropriate protocol such as SOAP(derived from the “Simple Object Access Protocol”). Processes providedor executed by such services can be written in any appropriate language,such as the Web Services Description Language (WSDL). Using a languagesuch as WSDL allows for functionality such as the automated generationof client-side code in various SOAP frameworks.

Most embodiments utilize at least one network that would be familiar tothose skilled in the art for supporting communications using any of avariety of commercially-available protocols, such as TCP/IP, OSI, FTP,UPnP, NFS, CIFS, and AppleTalk. The network can be, for example, a localarea network, a wide-area network, a virtual private network, theInternet, an intranet, an extranet, a public switched telephone network,an infrared network, a wireless network, and any combination thereof.

In embodiments utilizing a Web server, the Web server can run any of avariety of server or mid-tier applications, including HTTP servers, FTPservers, CGI servers, data servers, Java servers, and businessapplication servers. The server(s) also may be capable of executingprograms or scripts in response requests from user devices, such as byexecuting one or more Web applications that may be implemented as one ormore scripts or programs written in any programming language, such asJava®, C, C# or C++, or any scripting language, such as Perl, Python, orTCL, as well as combinations thereof. The server(s) may also includedatabase servers, including without limitation those commerciallyavailable from Oracle Microsoft®, Sybase®, and IBM®.

The environment can include a variety of data stores and other memoryand storage media as discussed above. These can reside in a variety oflocations, such as on a storage medium local to (and/or resident in) oneor more of the computers or remote from any or all of the computersacross the network. In a particular set of embodiments, the informationmay reside in a storage-area network (“SAN”) familiar to those skilledin the art. Similarly, any necessary files for performing the functionsattributed to the computers, servers, or other network devices may bestored locally and/or remotely, as appropriate. Where a system includescomputerized devices, each such device can include hardware elementsthat may be electrically coupled via a bus, the elements including, forexample, at least one central processing unit (CPU), at least one inputdevice (e.g., a mouse, keyboard, controller, touch screen, or keypad),and at least one output device (e.g., a display device, printer, orspeaker). Such a system may also include one or more storage devices,such as disk drives, optical storage devices, and solid-state storagedevices such as random access memory (“RAM”) or read-only memory(“ROM”), as well as removable media devices, memory cards, flash cards,etc.

Such devices also can include a computer-readable storage media reader,a communications device (e.g., a modem, a network card (wireless orwired), an infrared communication device, etc.), and working memory asdescribed above. The computer-readable storage media reader can beconnected with, or configured to receive, a computer-readable storagemedium, representing remote, local, fixed, and/or removable storagedevices as well as storage media for temporarily and/or more permanentlycontaining, storing, transmitting, and retrieving computer-readableinformation. The system and various devices also typically will includea number of software applications, modules, services, or other elementslocated within at least one working memory device, including anoperating system and application programs, such as a client applicationor Web browser. It should be appreciated that alternate embodiments mayhave numerous variations from that described above. For example,customized hardware might also be used and/or particular elements mightbe implemented in hardware, software (including portable software, suchas applets), or both. Further, connection to other computing devicessuch as network input/output devices may be employed.

Storage media and computer readable media for containing code, orportions of code, can include any appropriate media known or used in theart, including storage media and communication media, such as but notlimited to volatile and non-volatile, removable and non-removable mediaimplemented in any method or technology for storage and/or transmissionof information such as computer readable instructions, data structures,program modules, or other data, including RAM, ROM, EEPROM, flash memoryor other memory technology, CD-ROM, digital versatile disk (DVD) orother optical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other medium which canbe used to store the desired information and which can be accessed bythe a system device. Based on the disclosure and teachings providedherein, a person of ordinary skill in the art will appreciate other waysand/or methods to implement the various embodiments.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that various modifications and changes may be made thereuntowithout departing from the broader spirit and scope of the invention asset forth in the claims.

What is claimed is:
 1. A method, comprising: performing, with one ormore computing devices: receiving, from a user external to the one ormore computing devices, a service request to scale storage for areplicated database having a first instance replica and a secondinstance replica, wherein the replicated database is configured to applya write operation of the first instance replica to the second instancereplica; responsive to the received service request, scaling the storagefor the first instance replica and the second instance replica; and inresponse to a failure of the first instance replica, remapping a networkaddress of the first instance replica to the second instance replica,wherein after remapping, a received access request addressed to thenetwork address is transmitted to the second instance replica.
 2. Themethod of claim 1, further comprising executing a workflow via aworkflow service, wherein the workflow includes scaling the storage forthe first instance replica and the second instance replica.
 3. Themethod of claim 2, wherein the workflow service is configured to:generate a workflow task corresponding to the service request; andprovide a state for the workflow task.
 4. The method of claim 3, whereinthe workflow task includes at least one of: modifying an existing numberof respective block storage volumes of each of the first instancereplica and the second instance replica to a new number of block storagevolumes; causing one or more of the block storage volumes to berebalanced according to the new number of block storage volumes; causingone or more respective logical volumes for each of the first instancereplica and the second instance replica to be resized according to thenew number of block storage volumes; or causing a respective file systemfor each of the first instance replica and the second instance replicato be resized according to the new number of block storage volumes. 5.The method of claim 1, wherein the replicated database is furtherconfigured to apply the write operation of the first instance replica tothe second instance replica.
 6. The method of claim 5, furthercomprising resizing the replication mechanism based at least in part ona respective new configuration for each of the first instance replicaand the second instance replica.
 7. The method of claim 1, furthercomprising providing an interface configured to receive one or moreservice requests, wherein each of the one or more service requestscorrespond to a respective specified action to be performed at adatabase, and wherein the one or more service requests includes theservice request.
 8. The method of claim 1, wherein the network addressinformation includes a domain name system (DNS) name.
 9. The method ofclaim 1, further comprising causing the first instance replica tofailover to the second instance replica, wherein scaling the storage forthe second instance replica occurs prior to scaling the storage for thefirst instance replica.
 10. A method, comprising: receiving from a user,a service request to scale computing capacity for a replicated databasehaving a first instance replica and a second instance replica; inresponse to the received request, provisioning a third instance replicaand a fourth instance replica for the replicated database based at leastin part on a specified compute class indicated in the service request,wherein network address information corresponding to the third instancereplica is based on network address information corresponding to thefirst instance replica; and in response to a failure of the thirdinstance replica, remapping the network address informationcorresponding to the third instance replica, comprising remapping anetwork address of the third instance replica to the fourth instancereplica, wherein after remapping, a subsequently received access requestaddressed to the network address is transmitted to the fourth instancereplica.
 11. The method of claim 10, wherein the third instance replicaand the fourth instance replica are provisioned as part of a workflowservice, wherein the workflow service is configured to: generate aworkflow task corresponding to the service request; and provide a statefor the workflow task.
 12. The method of claim 10, further comprisingconfiguring the replicated database to apply any write operation of thethird instance replica to the fourth instance replica.
 13. The method ofclaim 10, further comprising causing the first instance replica tofailover to the third instance replica in response to provisioning thethird instance replica.
 14. The method of claim 13, wherein the thirdinstance replica is provisioned prior to provisioning the fourthinstance replica.
 15. A non-transitory computer-readable storage mediumstoring instructions that, when executed on one or more processors,cause the one or more processors to: receive, from a user, a servicerequest to scale storage for a replicated database having a firstinstance replica and a second instance replica, wherein the replicateddatabase is configured to apply a write operation of the first instancereplica to the second instance replica; responsive to the receivedservice request, scale the storage for the first instance replica andthe second instance replica; and in response to a failure of the firstinstance replica, remap a network address of the first instance replica,to the second instance replica, wherein after the remap is complete, asubsequently received access request addressed to the network address istransmitted to the second instance replica.
 16. The non-transitorycomputer-readable storage medium of claim 15, wherein the instructionsfurther cause the one or more processors to execute a workflow via aworkflow service in a control environment, wherein the workflow isconfigured to: generate one or more workflow tasks; and provide arespective state for the one or more workflow tasks.
 17. Thenon-transitory computer-readable storage medium of claim 16, wherein theone or more workflow tasks correspond to one or more host tasks to beperformed by one or more host managers in a data environment, andwherein the data environment is distinct from the control environment.18. The non-transitory computer-readable storage medium of claim 15,wherein the instructions further cause the one or more processors toresize a replication mechanism of the replicated database according to arespective new configuration for each of the first instance replica andthe second instance replica.
 19. The non-transitory computer-readablestorage medium of claim 15, wherein the instructions further cause theone or more processors to provide the network address of the firstinstance replica to enable access to the replicated database via thefirst instance replica.
 20. The non-transitory computer-readable storagemedium of claim 15, wherein the service request is based upon at leastone of a user request, user preferences, or configuration information.